1. Field of Invention
The present invention relates in general to testing equipment and more specifically to a portable device for the correct testing and marking of escalator step height variations.
2. Discussion of Prior Art
In the field of escalators, an escalator which has good step rollers, good rack axle rollers, and good rack axle hubs, there is no discernable variance of vertical height from the leading edge to the trailing edge of one step to the next. However, in an instance where an escalator step roller has lost diameter surface area, from approximately 1/16" to a maximum of the radius of a roller, improper operation may occur. The danger represented by a bad roller is very clear when considering the meshing of an escalator step with the comb finger sections is dependant on the proper diameter of escalator step rollers and rack axle rollers or rollers related to insuring proper step height at comb area.
The patent to Bartman (U.S. Pat. No. 5,236,075) discloses an escalator broken roller detector 10. The device utilizes proximity sensors 18, 20 in order to detect the diameter of each roller 22. The sensors 18, 20 emit a symmetrical signal which, when interrupted due to a roller 22 falling off its spool 32, will automatically trigger an alarm 38 and an escalator stop switch 40. See FIGS. 1, 2 and col. 2, lines 6-53.
The patent to Wente et al. (U.S. Pat. No. 5,096,040) discloses a device for detecting missing steps in an escalator. The system comprises a detector 12 having a pair of rollers 16 mounted on a carriage 20 that engage a side 28 of the steps 6. The carriage 20 is biased by a spring 42 such that if a step 6 is missing, the carriage 20 moves toward the steps 6 which in turn moves the switch button 34 thus shutting off the power to the escalator. See FIGS. 1, 2 and ABSTRACT.
The patent to Zaharia et al. (U.S. Pat. No. 5,316,121) discloses a system for detecting missing steps utilizing a proximity sensor 26. The system will cause the escalator to stop if the sensor 26 detects a missing or misaligned step 14, 16 by cutting off power to the motor 38 and activating the brake 40. See col. 2, lines 60+.
The patent to Nurnberg et al. (U.S. Pat. No. 5,255,771) disclose a complete safety device 34 that is mounted directly onto the combplate frame 40. See FIG. 2.
In today's escalator maintenance field, defective escalator rollers are typically found in one of the following ways. A maintenance mechanic may provide power to the escalator and walk the escalator, either at the landing (flat) area and step between the leading edge and trailing edge of two consecutive steps on the ball of his or her foot while attempting to "feel" differences in vertical distances as small as 1/16". Generally, this method is unreliable and physically tiring. Another method is to barricade the top and bottom of an escalator and open the top or bottom floor plate and visually inspect each of the rollers. However, unless a mechanic were to put a caliper on each roller, they will most likely not notice a roller which has lost 1/8" of diameter surface area. Most mechanics generally look for "flat" spots on rollers caused by roller bearing defects, which cause the wheel to drag thereby causing excessive wear to the roller. Both of the above described ways of detecting rollers are laborious, time consuming, and unreliable.
Each of the above methods fails to provide a low cost, portable device which will provide an immediate indication to a service repairman of not only that an roller and/or height error exists with one of the steps, but also exactly which step(s) has produced the error.